I would definitely not use your blackberry. Any phone that has a data plan will cost you astronomical amounts of money in international roaming. My phone even warns me about it and has a feature that I can turn off to avoid it. Just check out one guy's post on a previous thread where he was welcomed by a $1500+ phone bill when he got home.

I can receive texts on my U.S. phone for free from the U.S. and it costs me .50 to send one from Belize. What I do is have folks in the U.S. text me for free when they need to talk to me and then I call them back on the Belize phone. Best way I have found for me so far.